The present invention relates generally to signal processing in a communication system and more particularly to classifying an input signal as either voice or data.
For the most part, telecommunication systems were originally envisioned for voice signal transmission. Following its inception and implementation, however, pronounced changes have occurred in the telecommunication industry. Not only has voice communication via the telecommunication system become prolific through out the world, the presence of preexisting telephone lines has also made the telecommunication system a major media for data signal transmission. For example, many households and businesses in the United States and many foreign countries include telecommunication systems that are used for both the transmission of voice signals via a telephone and data signals via modem technology. As such, today""s telecommunication systems not only transmit an increasing number of voice signals, but are also used as a major throughput for data signals.
With the increased use of the telephone communication system for both voice and data signals, systems and methods have been developed to narrow the required bandwidth needed to transmit voice signals, such that more voice and data may be transmitted on existing telephone lines. For example, many of today""s telecommunication systems use encoding techniques to encode voice signals for transmission in telecommunication systems. These encoding techniques allow more information to be transmitted within the limited bandwidth of the telecommunication system.
Although encoding of voice signals is advantageous, implementation of voice encoding techniques in telecommunication systems can be somewhat problematic. Specifically, most telephone lines are used for both voice and data transmission. However, encoding techniques used for encoding of voice signals may introduce errors if used to encode data signals. In light of this, voice/data discrimination systems and techniques have been developed to discern voice and data signals, such that voice signals may be encoded, while data signals may be left unaffected or encoded by a different encoding procedure. These voice/data discrimination systems typically analyze signals transmitted on the telecommunication system and classify communication signals as either voice or data. Voice signals are then encoded prior to transmission to increase the amount of voice and data that may be transmitted in the telecommunication system.
Although conventional voice/data discrimination systems provide viable methods for voice and data signal discrimination, they do have some drawbacks. For example, one drawback with conventional voice/data discriminators is that they are typically computational intensive and may require an undesired amount of energy for voice/data discrimination. For example, many conventional voice/data discrimination systems use multipliers, dividers, Fast Fourier Transform systems, neural networks, and many other types of computational schemes to analyze signals transmitted on telecommunication systems and accurately characterize the signals as either voice or data. While these conventional voice/data discrimination systems typically provide a system for accurately characterizing communication signals as either voice or data, the energy consumed in analysis of the communication signals may be unacceptable.
Specifically, many telecommunication systems are comprised of either thousands or millions of communication lines used for transmission of both voice and data signals. A dedicated voice/data discrimination systems is typically needed to discriminate between voice and data for each communication line. Although the energy consumption of each individual voice/discriminator due to computationally intensive analysis of the signals may be negligible, the use of a plurality of these conventional voice/data discriminators in a telecommunication system may consume an unacceptable amount of energy. This may be particularly problematic in systems where energy conservation is at a premium.
An additional problem is that some conventional systems differentiate between voice and data signals based on specific characteristics of the data signals. Specifically, in many telecommunication systems, such as systems that use modems, an initial set of tones may be transmitted across the telecommunication line to inform systems that a data signal, as opposed to a voice signal, is being transmitted. In light of this fact, some conventional voice/data discrimination systems analyze the initial portion of a telecommunication signal and classify the signal as either voice or data based on whether these initial tones are present. While these conventional voice/data discrimination systems typically provide convenient apparatus and methods for discriminating between voice and data signals, they are somewhat limited. Specifically, these conventional voice/data discrimination systems must be activated prior to transmission of the telecommunication signal in order to classify the data as either voice or data.
As set forth below, the apparatus and method of the present invention may overcome many of the deficiencies identified with discriminating between voice and data signals in a communication system. In particular, the present invention provides apparatus and methods for classifying communication signals as either voice or data with a limited number of computational instructions, (i.e., multipliers, dividers, etc.), such that the communication signals may be classified with reduced energy consumption. Additionally, the present invention, provides apparatus and methods that may discriminate between voice and data signals based on the communication signal, as opposed to specific signal characteristics at the beginning of the signal. As such, the apparatus and methods of the present invention may classify a telecommunication signal as either voice or data without requiring activation prior to beginning transmission of the telecommunication signal.
The present invention provides several embodiments for classifying a communication signal as either voice or data in a communication system. For example, one embodiment of the present invention provides an apparatus and method for classifying an input signal based on both an estimation of the central frequency of an input signal and the energy level of the input signal. The apparatus of this embodiment includes a frequency estimator for generating a frequency estimate value representing both the estimated central frequency of an input signal and the estimate of the energy level of an input signal. The apparatus also includes an energy estimator for generating an energy estimate value representing an estimate of the energy level of the input signal. Additionally, the apparatus of this embodiment includes a classification unit in electrical communication with both the frequency and energy estimators for classifying the input signal as either a voice or data signal.
In operation, both the frequency and energy estimators receive the input signal and generate respective frequency and energy estimate values of the input signal. These estimate signals are received by the classification unit and compared to a data threshold value. If the frequency estimate value is at least as great as the data threshold value, the classification unit classifies the input signal as data. Otherwise, the input signal is classified as a voice signal.
Importantly the apparatus of this embodiment uses both the frequency and energy estimate of the input signal to classify the input signal as either voice or data. Because the present invention uses rough estimates of these values, as opposed to more accurate estimations provided by computational intensive systems, the apparatus and method of the present invention can typically classify the communication signal as either voice or data with less energy consumption. Additionally, because the present invention analyzes the communication signal, as opposed to initial tones appearing at the beginning of the signal, the apparatus and method of the present invention can typically classify the communication signal even if the apparatus and method of the present invention is activated during mid-transmission of the signal.
As discussed above, the present invention classifies the input signal based on both the frequency estimate and the energy estimate value of the input signal. In one embodiment, the present invention classifies the input signal based on an estimate of the central frequency of the input signal. To determine an estimate of the central frequency of the input signal, the classification unit of this embodiment further includes a normalizer in electrical communication with both the frequency and energy estimators. The normalizer generates an estimate of the central frequency of the input signal by comparing the frequency and energy estimate values generated by the frequency and energy estimators. Specifically, the frequency estimator of the present invention generates a composite signal representing both the estimated central frequency of the input signal and the estimated energy level of the input signal. The normalizer of this embodiment, compares the frequency and energy estimate values and generates a normalized frequency estimate value representing an estimate of the central frequency of the input signal.
To analyze the estimated central frequency of the input signal, the classification unit of this embodiment further includes a frequency detector in electrical communication with the normalizer. In this embodiment of the present invention, the frequency detector compares the normalized frequency estimate value generated by the normalizer to a data threshold value representing a threshold frequency value. Input signals having estimated central frequencies value equal to and above the data threshold value are considered data signals. As such, if the frequency estimate value of the input signal is at least as great as the data threshold value, the frequency detector classifies the input signal as data. Otherwise, the frequency detector classifies the input signal as voice.
As discussed, the classification unit of this embodiment includes a normalizer for normalizing the frequency estimate signal. In one embodiment of the present invention, the normalizer comprises a divider in electrical communication with both the frequency and energy estimators. In this embodiment of the present invention, the divider divides the frequency estimate value representing both an estimate of the central frequency of the input signal and the energy level of the input signal by the energy estimate value representing an estimate of the energy level of the input signal. As such, the normalizer generates a normalized frequency estimate value representing an estimate of the central frequency of the input signal.
As an alternative to the use of a normalizer, which may be energy consuming, the apparatus of the present invention may use an energy detector and a look-up table stored in a memory device to normalize the energy estimate signal. Specifically, in this embodiment, the classification unit of the present invention may include an energy detector in electrical communication with both the energy estimator and the frequency detector. Additionally, the classification unit of this embodiment may also include a look-up table stored in a memory device in electrical communication with the energy detector. The look-up table of this embodiment includes a plurality of differing data threshold values, each representing a selected threshold value for a given energy level of the input signal, (i.e., the selected threshold value multiplied by the given energy level).
In this embodiment of the present invention, the energy detector receives the energy estimation value and selects a frequency threshold value from the plurality of differing threshold values in the look-up table. Specifically, the energy detector selects the frequency threshold value corresponding to the energy level of the input signal. This frequency threshold value is supplied to the frequency detector of the classification unit. The frequency detector, in turn, uses the selected frequency threshold value to classify the input signal as either voice or data. Importantly, the classification unit of this embodiment uses a selected frequency from the look-up table to compensate for the energy level of the input signal, as opposed to the use of a normalizer. As such, the apparatus and method of this embodiment can typically classify the input signal with reduced computational instructions and reduced energy consumption due to the elimination of the normalizer.
As discussed above, the present invention typically classifies the input signal as either voice or data based on the estimated frequency value. However, in some embodiments, the present invention may initially evaluate the estimated energy level of the input signal to determine whether the input signal has sufficient energy for classification as a data signal. In this embodiment, if the input signal has an energy level that is less than a predetermined energy threshold value, the input signal is considered to have an insufficient energy level to be a data signal and classifies the input signal as voice, without further evaluating the frequency estimate value.
In this embodiment of the present invention, the classification unit further includes a switch in electrical communication with both the normalizer and the frequency detector for selectively connecting the normalizer and the frequency detector. The apparatus of this embodiment also includes an energy detector in electrical communication with the energy estimator and the switch. In operation, the energy detector initially compares the energy estimate value to an energy threshold value defining a predetermined minimum energy level. If the energy estimate value is less than the energy threshold value, the energy detector classifies the input signal as voice and the frequency estimate value is not further analyzed by the frequency detector. However, if the energy estimate value is at least as great as the energy threshold value, the energy detector controls the switch to connect the normalizer and the frequency detector, such that the frequency detector analyzes the frequency estimate value and classifies the input signal as either voice or data.
As detailed above, the present invention includes a frequency estimator for generating a frequency estimate value representing both the estimated central frequency of the input signal and the estimated energy level of input signal. In one embodiment of the present invention, the frequency estimator generates the frequency estimate value by taking the derivative of the input signal. To take the derivative of the input signal, the frequency estimator of this embodiment includes a delay in electrical communication with the input signal and a difference integrator in electrical communication with both the delay and the input signal. In operation, the delay receives the input signal and generates a delayed input signal. The difference integrator, in turn, receives the delayed, as well as the input signal and generates a frequency estimate value representing both the estimated central frequency of the input signal and the estimated energy of the input signal. This frequency estimate value is used by the classification unit as previously described above to classify the input signal as either voice or data.
In a further embodiment of the present invention, the frequency estimator may also include an absolute value device and an accumulator in electrical communication with the difference integrator. In this embodiment of the present invention, the absolute value device receives the frequency estimate value and generates an absolute value of the frequency estimate value and the accumulator device generates a smoothed or filtered frequency estimate value.
As detailed above, the present invention includes an energy estimator for generating an estimate of the energy level of the input signal. In one embodiment of the present invention, the energy estimator may also include an absolute value device and an accumulator in electrical communication with the input signal. In this embodiment of the present invention, the absolute value device receives input signal and generates an absolute value of the input signal and the accumulator device generates a smoothed or filtered energy estimate value.
As briefly discussed above and detailed in the various embodiments below, the present invention provides apparatus and methods for classifying communication signals as either voice or data with a limited number of computational instructions, (i.e., multipliers, dividers, etc.), such that the telecommunication signals may be typically classified with reduced energy consumption. Additionally, the present invention, provides apparatus and methods that may discriminate between voice and data signals based on the communication signal, as opposed to specific signal characteristics at the beginning of the signal. As such, the apparatus and methods of the present invention may classify a telecommunication signal as either voice or data without the prerequisite of the apparatus and method of the present invention being activated prior to beginning transmission of the communication signal.